I've been thinking about this "not lost - just stagnant" thing the last week, unfortunately, I don't think it's actually true. You are always losing or gaining depending on what you are comparing to. If the economy is measured by the market, then it costs you more to get in later, it's effectively the same as losing.
Sure, you may not be losing on purchasing power of staple goods, but on almost any scale where an investment is valuable, you are losing, unless you can get in at the net crash. Just a different perspective.
You might have noticed a whole lot of stocks dropped today. If I had my float money on some other stocks instead, they would have lost along with the rest. Instead, because it was liquid, I was able to buy at today's lows. Mainly today I bought more of some shares I already own because they were down a fair amount (bought pre-covid), and today's purchase made the loss a much smaller percent. Eventually the markets will rebound and I'll have a lot of money there and a much shorter route to green territory.
To avoid fees, I have to make 2 trades a quarter minimum. I consider those fees to be losses, even though they aren't terribly substantial. So there is also that incentive to keep a float and wait for good moments like today for buys. There's no reason to buy immediately just because I got paid today.
I'm not done for the day yet. But that's why I say stagnant and not lost. It's more than just the one-phrase simplification I originally posted, as I was just focusing on that one aspect of it.
Sure, you may not be losing on purchasing power of staple goods, but on almost any scale where an investment is valuable, you are losing, unless you can get in at the net crash. Just a different perspective.